Windows 7: MBR - Restore Windows 7 Master Boot Record

On some other forum, I found out someone had a similar issue as I did. Some virus or malware infected the system (as well as Microsoft Security Essentials or Windows Defender - it's on auto update so dont know which is running at the time).

I get a warning that there's an infection, and suddenly, BAM! Blue screen with these words: UNKNOWN HARD ERROR! And that's that. Restarted it, and it would always boot in repair mode.

I said THERE WE GO. Ironic as it is, windows backup or system restore have never worked out for me - EVER. So i knew i'd have to reinstall Windows. Not even auto repair, or the stupid auto recovery disk does anything.

And then I landed here. 4 minute later, I was back on my desktop.

Thanks, Thread starter! You just saved my day!

You are most welcome. Thanks for letting us know you found a solution here. Welcome to Windows Seven Forums.

Cheers!
Robert

I wanted to 'reverse' an EasyBCD-controlled dualboot (XP Pro, then Windows 7) and use GAG for individual OS booting, 'coz I'm adding another XP for audio editing.
At the start of this thread, Robert (iseeuu) suggested using bootsect to modify the master boot record. I didn't realise this was possible; were you referring to the actual MBR in the first sector of the hard drive, or to the 'master boot sector' in the system volume?
Bye the way, thanks for your detailed, excellent descriptions - a great service!
Chris
PS - any tips on untangling my XP and Windows 7 . . . ?

Hello RumJungleMusic, and welcome to Windows Seven Forums.

As to your first question: I like to think of a hard drive as a room full of file cabinets. You could of course just cut a hole in the ceiling and drop your files into the room from there. But how would you ever find anything. The master boot record tells the computer what kind of filling system is placed on the hard drive, as in the example: how many cabinets, drawers, and files and how and where to find them when the computer boots. Boot loaders like LILO and Grub over write the windows boot loaders in the MBR when they are installed. This tutorial shows how to put the Windows boot loaders back. No other changes are made to the MBR.

It is the boot loader that looks for the partition or volume marked "Active" so it can start the computer. If I understand you, the "Active Flag" is in what you described as the "master boot sector" of the individual partitions or volumes and other than being turned on or off, no changes are made to that sector.

As to your second question: we would have to know how you installed 7 in order to help you "untangle" the two. If you left the XP partition "Active" when you added 7, then most likely Windows 7 put its boot files in the XP partition. If you installed 7 by itself via a default factory install and allowed 7 to create the 100MB "System Reserved" partition to hold the boot files, different steps would be needed. In any case it is not likely that you would need to change the MBR, as you are still only using windows and your choice of new boot loader should place its own correct boot code in the correct place.

I would suggest you create a new thread with your question on how best to separate your current dual boot and include a "Screen Shot" of your Window hard drive map so we can see what you have?

Cheers!
Robert

Wow! Thank you for this. This tutorial saved me.

Followed every step.

Target volumes will be updated with BOOTMGR compatible boot code.
The system partition was not found:
The requested system device cannot be found.

Any tips?

THANK YOU!!

This worked perfectly! I was afraid I lost my Windows partition

OK i have followed the instructions and i got rid of error no such partition and now everything OK accept i cannot access boot options from windows route msconfig and through pressing f8 advanced boot options please help me

THANK YOU. Worked perfectly, after all else failed. You are my hero.